Help me get this right about DolbyD,DTS, Dvd-audio etc.

Discussion in 'AV Receivers' started by Billy Posey, Sep 17, 2006.

  1. Billy Posey

    Billy Posey Second Unit

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    Help me get this right about Dolby Digital, DTS, DolbyTrue HD, DTS HD, Sacd, Dvd audio, Uncompressed audio.


    I will make some statements and their relations and hopefully you guys will tell me if I am right or wrong. I will start with the obvious.

    Example A: LP or vinyl.

    Stereo sound is stored on the media format in a left channel right channel. The same as cassettes or even stereo vhs.


    Example B: Compact disc

    Stereo sound in digital form but needs to be converted to analog left and right channels.

    Example C: DVD more notably Dolby Digital, DTS, DTS HD, Dolby True HD, Dolby Digital Plus. Compression algorithms.

    sound in digital form compressed using one of these schemes. Must be decoded either in player or receiver/prepro then converted to from digital to multiple analog channels


    Example D: Sacd DVd Audio Uncompressed Audio( blue ray /HD dvd)


    HI Rez sound in digital form must be converted to multiple analog channels by player or Receiver/pre pro ( after being transmitted via HDMI because of copy right issues).

    Let me know if I am wrong any where.
     
  2. Seth=L

    Seth=L Screenwriter

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    I don't understand what you are asking. Are you asking if you are accurate in the description of these different forms of audio compression?
     
  3. Seth=L

    Seth=L Screenwriter

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    DVD-Audio uses Losseless as well do forms of TrueHD and DTS-HD, I beleive they are called master audio tracks. Blu-Ray currently uses uncompressed 5.1 192khz/24bit LPCM. DVD-audio uses Lossless packing called PPCM 96khz/24bit in 5.1 and 192khz/24bit in stereo. I think, though someone correct me if I am wrong, but Dolby TrueHD uses a similar if not the same format as DVD-audio.

    SACD is a different animal all together. It was made using Sony's technology called DSD (direct stream digital) which is one competitor to standard PCM. It is argued that DSD has more noise distortion and was never implemented as the standard for CD's. I think that SACD was DSD's last stand, as I do not believe it will be adopted by Blu-Ray.

    LP, or vinyl, still holds the highest possible quality of all current formats. It never has to be converted from digital to analog, and isn't affected by magnetism as with tapes. Tapes in general don't have tons of potential anyway. Vinyl has a wide frequeny range as well, a full octave below CD I know. With a high quality playback system and an undamaged, well mastered LP then no format can come even close to the perfect sound of a prestine LP.
     
  4. Billy Posey

    Billy Posey Second Unit

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    Basically I am trying to find out what exactly is going on with Dvd-audio,SACD, and the new formats used with HD-DVD or Blue-ray. As I understand it Vinyl records, cassette tapes, and Compact discs were able to hold the Left and Right channels of a stereo signal. But when is came to having multiple channels of sound there wasn't enough room to have all the channels on a compact disc or dvd so they had to compress it using Dolby Digital or DTS codec which would then be umcompressed or decoded using a processor in the source player or Receiver/Pre pro. What I am not sure of is when it comes to DVD-audio, SACD or the The new formats Dolby True Hd or DTS HD. Are they new ways to put multiple channels of sound/music on a disc without needing to compress it or are they new and improved compression codecs.

    Here is what I think but maybe wrong about. Often I hear about dvd players being able to pass Dvd- audio/Sacd through either I-links or HDMI. Now is it a codec that needs to be decoded by a codec processor in the receiver/Pre Pro? or is it just the same as connecting the six analog outputs of a dvd-audio/SACD player only in digital form. Similar to a cd player using a digital out to use a receivers a/d circuits. The latter seems to be the case as I read it but I'm not sure.

    Dolby True HD and DTS HD seem to be compression scheme ( although a lossless version but What I am confused about is when I read about the new Players HD-DVD and Blue ray it seems that they can't pass a Dolby True HD or DTS HD signal but it can pass umcompressed multichannel audio. If it can do that then why do we need The new formats? Isn't that what we wanted anyway a discreet Left Channel, Right Channel, Center channel, Right rear, Left rear etc. All on the disc.


    I remember back when I was first reading about how dolby prologic work, I can wanted to ask why don't just put all the channels of a soundtrack on the disc or tape. while searching I saw a diagram on how LPs worked. The enlarged image of the groves that are on the record. These groves were v-shaped like in which the needles fit in to. both sides of the v-shape grooved had ridges which pretty much the physical form of the soundtrack. The ridges vibrated the needle with through a process translated into sound. One side of the ridges would be for one channel and the other side would be for well, the other channel. I thought that the cassette was a magnetic tape version of this process and the compact discs pits was the 1s and 0s way of doing this digitally. And I thought that the answer to my question of why just not put all the channels on the media format was because there wasn't room to do so. That's why we had the pro logic matrixing, Dolby Digital and DTS codec compression so that we could get pass the limitations. But if this uncompressed multi-channel audio on these new HD-dvd/Blue ray disc the same as having a "groove" for all the channels of a particular soundtrack, the what's the point of the compression codecs?
     
  5. Seth=L

    Seth=L Screenwriter

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    Standard Dolby Digital is more compressed than CD. Standard DTS is similar on compression to CD. TrueHD, DVD-audio, SACD, and DTS-HD are far superior to CD in just about all ways mathematically, assuming the transfers are good. The issue is, can we tell the difference, maybe, maybe not.
     
  6. Billy Posey

    Billy Posey Second Unit

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    I didn't think cd(pcm) was compression.
     
  7. Seth=L

    Seth=L Screenwriter

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    Of course it is. If it wasn't compressed then we would call DVD-audio uncompressed which it isn't. SACD, DVD-audio, TrueHD, DTS-HD these formats have less compression than CD. There really isn't a such thing as completely uncompressed.
     
  8. Billy Posey

    Billy Posey Second Unit

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    Compact discs only need Digital to analog conversion correct?

    Dolby Digital and DTS needs to be decoded then digital to ananlog conversion correct?

    How about DVD-Audio/SACD? I Know that in players like mine the digital signal is converted to analog in the player, but what about those that send the signal to a receiver through an I-link or HDMI input. Is the receiver decoding the signal then converting from Digital to analog or does the receiver simply need to do D/A conversion?
     
  9. FeisalK

    FeisalK Screenwriter

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    DVD-Audio is compressed PCM (Packed PCM) using a process called Meridian Lossless Packing

    first time I've heard of CD's being compressed in this context - the dynamic range is compressed nowadays, but not the PCM signal as far as I know
     

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